1. Field of the Invention
The invention concerns an apparatus for detaching meat from the skeletons of fish, particularly in the region of the ribs, after belly and back cuts have been performed adjacent the belly and back spokes to cut these free, the apparatus comprising conveying means for transporting the fish in a conveying direction, lower and upper guide means defining guiding surfaces and guide edges, the lower and upper guide means being arranged to extend into the belly and back cuts to enclose the belly and back spokes, respectively, and being separated by a first gap which is limited by the guide edges, such that the latter guide the ribs or lateral vertebral appendages at their point of attachment to the vertebral column; a tool for freeing the ribs and comprising scraping knives having pointed ends and counter supports for the scraping knives, the scraping knives being arranged one on each side of the fish path and inclined towards one another with the pointed ends being directed against the conveying direction, and having a cutting edge, the counter supports being arranged to oppose the cutting edges, respectively, and being separated from the cutting edge by a second gap; and controlling means for controlling the scraping knives such that their points are moved out of a position adjacent the lower guide means into a position adjacent the upper guide means shortly before the arrival of the leading end of the fish ventral cavity.
2. Prior Art
Detaching meat using a scraping process, particularly in the region of the ribs, is known and due to the high yield attainable with this process is successfully used mainly in the filletting of middle-sized and large fish. For example a device is disclosed in DE-PS 29 46 042 which has a scraping tool with the above described features at its heart.
In the mechanical processing of fish, it is important, particularly with regard to the economical aspects of processing, that the corresponding processing machines are able to take account of a certain size range within a particular species of fish, or even different fish species with differently shaped belly cavities and lateral bones with the minimum of disruption. This may be achieved with modern imaging and control means, however, in view of the presently existing environmental demands these means are not ideal because of their cost and the problems associated with their maintenance. As a result, there is a tendency to try and achieve an attractive universal solution with simple mechanical means.
However, it has been observed in practice that attempts to follow this principle result in unsatisfactory limitations, particularly with respect to the step of rib scraping, which principally results in individual ribs or fragments thereof remaining in the fillet meat around the end of the belly cavity. This is particularly true when fish are processed which differ from the average size, or exhibit a critical consistency such as thawed frozen goods.
Precise examination has shown that this is caused by the stiffness exhibited by the scraping tool in the known arrangement which is unable to prevent such an error by conforming flexibly to the fish being processed. However, this tool is subjected to high demands which make its robust construction and solid anchorage essential requirements.
Experiments have shown that the frequency of occurrence of the above error is markedly reduced when the scraping blade is arranged to be elastically resilient to a certain extent in a plane lying perpendicular to the plane of symmetry of the fish, i.e. in a plane which in the known arrangement brings about a rigid association.
This requirement results in the scraping blades as described in DE-PS 29 46 042 being controlled to move over the vertebrae to insert their points into the region between the back spokes and the rib bases or vertebral appendages shortly before the arrival of the rear end of the ventral cavity in order to activate the scraping blades. Due to constructional limitations, this was achieved by swinging the scraping tool in a plane lying parallel to the plane of symmetry of the back and belly guides. In the known arrangement, the thickness dimension of the vertebrae of the largest fish to be processed at the position of activation of the scraping blades is decisive for setting the spacing between the points of the scraping blades. It is thus apparent that ideal conditions only exist for fish of a very limited size range so that the frequency of occurrence of the above described errors must increase when fish lying outside this range are processed.
3. Objects of the invention
It is thus an object of the invention to provide an apparatus capable of processing a large range of fish sizes and/or fish species without waste and with uniform quality.
It is a further object of the invention to improve prior art apparatus such that fishes of different sizes and species may be processed successfully without substantially increasing the cost or complexity of the apparatus.